Pumps and compressors which use moving pistons are extremely well known in the art. Typically, the piston is connected to a crank. The piston reciprocates in a cylinder and the reciprocating action results in pumping fluid which passes into the cylinder. The pump is typically electrically powered, powered by an internal combustion motor and the like. One disadvantage with this type of pump is that pumping occurs only when piston is in the compressive stroke. When the piston is in the drawdown stroke, no pumping occurs as the drawdown stroke is required to suck additional fluid into the cylinder or housing. Therefore, half the action of the piston does not contribute to the pumping action. Another disadvantage with existing piston pumps is that the piston has a short stroke and this results in increased wear and tear of the pump. Moreover, these types of pumps generally suffer from excessive noise levels making them unsuitable in many applications.
A conventional piston in a cylinder has about a 1:1 bore to stroke ratio. For instance, if the bore has a diameter of 60 mm, the piston stroke is also approximately 60 mm. An advantage of the apparatus of the present invention is that the “piston” to “bore” ratio can be 7:1, 10:1, or even larger. Thus, the apparatus can have approximately 10 times the stroke of a conventional piston in a cylinder. This allows the apparatus to work at lower speeds, provides lower wear and reduces the noise during use of the apparatus.
It will be clearly understood that, any prior art publications referred to herein, do not constitute an admission that any of these publications form part of the common general knowledge in the art in Australia or in any other country.